Standard and Multi-Frequency Echo Sounders, also called Multi-Beam SONAR,
allow scientists to accurately image the shape of the ocean floor, as
well as densities of marine animals in the water column. Unlike standard
Side-Scan SONAR, which produces a flat image with shadows denoting the shape
of the seafloor, this type of acoustic technology produces a more fully rendered image that
covers a wide swath of the benthos, providing a more detailed image, as
well as more accurate measures of water depth.

The towed body housing the Echo Sounder used for the observation of fish and plankton, even at great depths. (Mid-Atlantic Ridge Ecosystems - MAR-ECO)